Hydrogen Generation from Eosin Y-sensitized Pt/ZnO under Solar Light Irradiation

94 Pages·2017·1.89 MB·English

Western University
Abstract
Hydrogen is a promising alternative energy carrier. Generating hydrogen via photocatalysts
is clean and energy saving comparing to the current technology for hydrogen generation.
ZnO has been proved to have photocatalytic activities for wastewater treatment by multiple
studies. However, there are not enough studies to investigate its potential to generate
hydrogen as the photocatalyst under light irradiation. Therefore, we will investigate the
photocatalytic ability of Pt/ZnO to generate hydrogen. Triethanolamine (TEOA) was used as
sacrificial reagent while Eosin Y was used as sensitizer.
Pt/ZnO was characterized and tested for its activity for hydrogen generation in diffe rent
conditions, which are platinum loading, pH value, EY to catalyst mass ratio, photocatalyst
loading, TEOA concentration and light intensity.
The results showed that 0.75w% Pt/ZnO exhibited highest activity with hydrogen generation
-1
rate of 6.504 μmol min under solar light irradiation.
Keywords
Photocatalysis, metal loading, hydrogen generation, solar, co-catalyst, platinum.

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Acknowledgments
First, I would like to give my sincere gratitude to my supervisor Prof. Ajay K. Ray for his
kind instruction, sincere help and understanding. Whenever I have confusion, he will always
be willing be guide me with enormous patience and intelligence.
I would also like to thank my parents for their unconditional supports so that I could always
face the difficulties with a big and strong heart. Their love provides me with warmth and
safety that accompany me to study and live in a different country.
My colleagues Malini, Manoli, Daria and Mrinmoyee were always so helpful when I was
working for my subject. They never hesitate to give me their hands whenever I need help and
supports. Thank you for all the help and instructions all these years.
I would also express my sincere gratitude to technical stuff: Pastor Solano-Flores, Ying
Zhang and Venkateswara Reddy Kandlakuti for giving me technical supports through my
research.
Finally, thank you my dear friends. Thank you for your company and the happiness that you
brought to me during my staying. Without you, I would never make it.
I feel so blessed to have all the supports, help and love with me through all these years!

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Table of Contents

Abstract ................................................................................................................................ i
Acknowledgments............................................................................................................... ii
Table of Contents ............................................................................................................... iii
List of Figures .................................................................................................................... vi
Nomenclature ................................................................................................................... viii
Dedication .......................................................................................................................... ix
Chapter 1 ............................................................................................................................. 1
1 Introduction .................................................................................................................... 1
1.1 Background and motivation .................................................................................... 1
1.2 Thesis objective & structure ................................................................................... 3
1.3 References: .............................................................................................................. 6
Chapter 2 ........................................................................................................................... 11
2 Review.......................................................................................................................... 11
2.1 Basic principles of water splitting via semiconductor .......................................... 12
2.1.1 Properties of semiconductors .................................................................... 12
2.1.2 Sacrificial reagent systems ...................................................................... 16
2.1.3 Z-scheme system ..................................................................................... 18
2.2 Photocatalyst modification.................................................................................. 19
2.2.1 Metal deposition...................................................................................... 20
2.2.2 Binary composites coupling .................................................................... 21
2.2.3 Doping.................................................................................................... 23
2.2.4 Carbon nano-material hybridization ........................................................ 25
2.2.5 Dye-sensitized of photocatalysts.............................................................. 26
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2.3 Methods of photocatalyst modification ................................................................ 28
2.3.1 Photo-deposition ....................................................................................... 28
2.3.2 Impregnation ............................................................................................. 29
2.3.3 Chemical reduction ................................................................................... 30
2.3.4 Electrodeposition ...................................................................................... 31
2.3.5 Atomic-layer deposition............................................................................ 31
2.4 Conclusions ........................................................................................................... 32
2.5 References: ............................................................................................................ 33
Chapter 3 ........................................................................................................................... 53
3 Sacrificial Hydrogen Generation from Eosin Y-sensitized Pt/ZnO Under Both Solar
and Visible Light Irradiation ........................................................................................ 53
3.1 Introduction ........................................................................................................... 53
3.2 Experimental Section ............................................................................................ 55
3.2.1 Chemicals .................................................................................................. 55
3.2.2 Preparation of Pt/ZnO ............................................................................... 55
3.2.3 Photocatalytic characterization ................................................................. 56
3.2.4 Photocatalytic experiment ......................................................................... 56
3.3 Results and discussion .......................................................................................... 57
3.3.1 Characterization of Pt/ZnO ....................................................................... 57
3.3.2 Possible mechanism of hydrogen generation from Pt/ZnO ...................... 62
3.3.3 Effect of platinum loadings on photocatalytic activity of ZnO ................ 63
3.3.4 Effect of solar and visible light intensity on hydrogen generation rate .... 65
3.3.5 Effect of initial pH on photocatalytic activity of Pt/ZnO ......................... 66
3.3.6 Effect of initial TEOA concentration ........................................................ 67
3.3.7 Effect of EY concentration ....................................................................... 69
3.3.8 Effect of photocatalyst loading ................................................................. 70
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3.3.9 Regression analysis of experimental data ................................................. 71
3.4 Conclusions ........................................................................................................... 75
3.5 References: ............................................................................................................ 76
4 Conclusions and recommemdations ............................................................................. 83
Curriculum Vitae .............................................................................................................. 84

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List of Figures
Figure 2.１Principles of water splitting via semiconductors ................................ .................. 13
Figure 2.２Band gap potential of semiconductors ................................ ................................ . 14
Figure 2.３Schematic of the principles of water reduction or oxidation in sacrificial agent
system ................................ ................................ ................................ ................................ ..... 18
56
Figure 2.４Schematic of the principles of overall water splitting in the Z -scheme system 19
Figure 2.５Schematic of the energy band model of a Schottky junction (Ef represents fermi
energy level, Ec and Ev represent conduction band energy level and valence band energy
level) ..................................................................................................................................... 21
Figure 2.６One typical type of heterojunction structure of semiconductors .......................... 23
142
Figure 2.７Schematic diagram of dye-sensitized photocatalysts under light illumination
and possible backward reaction pathway (dotted line) .......................................................... 28
Figure 3.１XRD of 0.75 w% Pt/ZnO ..................................................................................... 58
Figure 3.２XRD of pure ZnO ................................................................................................. 58
Figure 3.３DRS of 0.75 w% Pt/ZnO and ZnO ................................ ................................ ....... 59
Figure 3.４SEM of 0.75 w% Pt/ZnO ................................ ................................ ...................... 60
Figure 3.５EDX of ZnO and 0.75 w% Pt/ZnO ................................ ................................ ...... 61
Figure 3.６Dependence of Pt loading to hydrogen generation rate ................................ ........ 64
Figure 3.７Dependence of solar and visible light intensity to hydrogen generation .............. 65
Figure 3.８Dependence of pH value to hydrogen generation rate ........................................ 66
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Figure 3.９Dependence of volume concentration of TEOA to hydrogen generation ............ 68
Figure 3.１０Dependence of weight ratio of EY to Pt/ZnO to hydrogen generation rate ..... 70
Figure 3.１１Dependence of catalyst dosage to hydrogen generation rate............................ 71
Figure 3.１２Group 1 fitted line of (a) solar intensity (b) catalyst dosage to hydrogen
generation rate ......................................................................................................................... 72
Figure 3.１３Fitted line of (a) content of Pt and (b) pH to hydrogen generation rate ........... 73
Figure 3.１４Fitted line of EY concentration to hydrogen generation rate ........................... 74
Figure 3.１５Normal probability plots of the residuals for H2 generation rate where a) light
intensity b) TEOA concentration are predictor variables ....................................................... 74

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Nomenclature
-1
C0 initial concentration (g l )
Dye* excited state of dye
+
Dye oxidized form of dye
-
e electron
EY eosin Y
ΔG Gibbs free energy
+
h excited hole
h plank’s constant
k reaction rate constant
K absorption constant
λ wavelength of light (nm)
-1
ν frequency (s )
μmol micromole
TEOA triethanolamine
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Dedication
To my dear parents and friends
Love you all

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